Hibernate尝试两次持久保存同一个对象

Question

我有3个类对应3个表V,D和P.D有一个FK到V(FK_V)并使用OneToMany关系加入.也是他们退出4台 V_D_P具有的这些关系V,D和P.

以下是这些数据模型的样子:

@Entity
@Table(name = "V")                                                   
public class V {

     @Id
     @GeneratedValue(strategy = GenerationType.SEQUENCE)
     @Column(name = "ID")
     private Long id;

    @OneToMany(cascade=CascadeType.ALL)
    @JoinColumn(name = "FK_V", referencedColumnName="Id", nullable = false)
    private Set<D> d;

    @OneToMany(cascade=CascadeType.ALL)
    @JoinColumn(name = "FK_V", referencedColumnName="Id", nullable = false)
    private Set<V_D_P> vdp;

    //Getters Setters etc.
}


@Entity
@Table(name = "V_D_P")
public class V_D_P {

      @Id
      @GeneratedValue(strategy = GenerationType.SEQUENCE)
      @Column(name = "ID")
      private Long id;

     @ManyToOne(cascade=CascadeType.ALL)
     @JoinColumn(name = "FK_D", nullable = false)
     private D d;

     @ManyToOne(cascade=CascadeType.ALL)
     @JoinColumn(name = "FK_P", nullable = false)
     private P p;

     //Getters Setters etc.       
}

@Entity
@Table(name = "D")                                                   
public class D {
      @Id
      @GeneratedValue(strategy = GenerationType.SEQUENCE)
      @Column(name = "ID")
      private Long id;

    //Getters Setters etc.
}

@Entity
@Table(name = "P")                                                  
public class P {

      @Id
      @GeneratedValue(strategy = GenerationType.SEQUENCE)
      @Column(name = "ID")
      private Long id;

    //Getters Setters etc.
}

现在我想坚持下去V,D以及P他们的关系.我是

V v = new V();

D d = new D();
Set<D> dSet = new HashSet<>();
dSet.add(d);
v.setD(dSet); // Adding d to V ....(1)

P p = new P();
V_D_P vdp = new V_D_P();

vdp.setD(d); // Adding d to V_D_P ....(2)
vdp.setP(p);

Set<V_D_P> vdpSet = new HashSet<V_D_P>();
vdpSet.add(vdp);
v.setVdp(vdpSet);

entityManager.persist(v);

现在你可以看到我正在添加d两次相同的对象.一次到P,一次到V_D_P.但是,由于它们是相同的对象,因此只能存在一次.但是根据hibernate日志,我看到hibernate试图插入2个不同的对象.

我还看到以下异常:ORA-00001:唯一约束

有没有办法让hibernate这些是相同的对象并且只持有它们一次？

Answer 1

对象由id唯一标识.因此他们必须具有相同的ID.

• 要么之前提供id,
• 或保留一次并d在保存另一个之前刷新对象(因此它设置了id).